A Case of Leukemic Pleural Infiltration in the Blast Crisis Phase of Chronic Myeloid Leukemia: An Unusual Extramedullary Involvement.

The development of pleural effusion in chronic myeloid leukemia (CML) is not well-understood and rarely documented in literature. Extramedullary involvement (EMI), which occurs in about 10% of CML cases, typically affects lymph nodes and the spleen. Instances of extensive infiltration of leukemic cells into the pleura are infrequently reported in CML. Here, we report a case of 41-year-old man experiencing significant bilateral pleural effusion with leukemic infiltration during the blast crisis (BC) phase of refractory CML. Examination of the pleural fluid revealed cells with morphological characteristics of myeloblasts. Although very rare, pleural leukemic infiltration should be considered as a cause of pleural effusion in patients with CML, especially in the BC phase.